Submission #3236465

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Source Code Expand

#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;

const double PI = 3.1415926535897932384626433832795;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { -1, 0, 1, 0 };

int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
int lcm(int x, int y) { return x / gcd(x, y) * y; }
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);


	int n;
	cin >> n;

	vector<int> a(n);
	for (auto &v : a) {
		cin >> v;
		v--;
	}

	int cnt = 0;
	for (int i = 0; i < (int)a.size(); i++) {
		int love = a[i];
		if (i == a[love]) {
			cnt++;
		}
	}

	cout << cnt / 2 << endl;
	return 0;
}

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